-----------------------------------------------------------------------------
--
-- | Parsing the top of a Haskell source file to get its module name,
-- imports and options.
--
-- (c) Simon Marlow 2005
-- (c) Lemmih 2006
--
-----------------------------------------------------------------------------

module Eta.Main.HeaderInfo ( getImports
                  , mkPrelImports -- used by the renamer too
                  , getOptionsFromFile, getOptions
                  , optionsErrorMsgs,
                    checkProcessArgsResult ) where

import Eta.BasicTypes.RdrName
import Eta.Main.HscTypes
import Eta.Parser.Parser           ( parseHeader )
import Eta.Parser.Lexer
import Eta.Utils.FastString
import Eta.HsSyn.HsSyn
import Eta.BasicTypes.Module
import Eta.Prelude.PrelNames
import Eta.Utils.StringBuffer
import Eta.BasicTypes.SrcLoc
import Eta.Main.DynFlags
import Eta.Main.ErrUtils
import qualified Eta.Main.ErrUtils as ErrUtils
import Eta.Utils.Util
import Eta.Utils.Outputable
import qualified Eta.Utils.Outputable as Outputable
import Eta.Utils.Pretty           ()
import Eta.Utils.Maybes
import Eta.Utils.Bag              ( emptyBag, listToBag, unitBag )
import Eta.Utils.MonadUtils
import Eta.Utils.Exception
import qualified Eta.Utils.Exception as Exception
import qualified Eta.LanguageExtensions as LangExt
import Control.Monad
import System.IO
import System.IO.Unsafe
import Data.List

------------------------------------------------------------------------------

-- | Parse the imports of a source file.
--
-- Throws a 'SourceError' if parsing fails.
getImports :: DynFlags
           -> StringBuffer -- ^ Parse this.
           -> FilePath     -- ^ Filename the buffer came from.  Used for
                           --   reporting parse error locations.
           -> FilePath     -- ^ The original source filename (used for locations
                           --   in the function result)
           -> IO ([(Maybe FastString, Located ModuleName)],
                  [(Maybe FastString, Located ModuleName)],
                  Located ModuleName)
              -- ^ The source imports, normal imports, and the module name.
getImports dflags buf filename source_filename = do
  let loc  = mkRealSrcLoc (mkFastString filename) 1 1
  case unP parseHeader (mkPState dflags buf loc) of
    PFailed span err -> parseError dflags span err
    POk pst rdr_module -> do
      let _ms@(_warns, errs) = getMessages pst
      -- don't log warnings: they'll be reported when we parse the file
      -- for real.  See #2500.
          ms = (emptyBag, errs)
      -- logWarnings warns
      if errorsFound dflags ms
        then throwIO $ mkSrcErr errs
        else
          case rdr_module of
            L _ (HsModule mb_mod _ imps _ _ _) ->
              let
                main_loc = srcLocSpan (mkSrcLoc (mkFastString source_filename) 1 1)
                mod = mb_mod `orElse` L main_loc mAIN_NAME
                (src_idecls, ord_idecls) = partition (ideclIsSource.unLoc) imps

                     -- GHC.Prim doesn't exist physically, so don't go looking for it.
                ordinary_imps = filter ((/= moduleName gHC_PRIM) . unLoc . ideclName . unLoc)
                                       ord_idecls

                implicit_prelude = xopt LangExt.ImplicitPrelude dflags
                implicit_imports = mkPrelImports (unLoc mod) main_loc
                                                 implicit_prelude imps
              in
              return (ideclsSimplified src_idecls,
                      ideclsSimplified (implicit_imports ++ ordinary_imps),
                      mod)

mkPrelImports :: ModuleName
              -> SrcSpan    -- Attribute the "import Prelude" to this location
              -> Bool -> [LImportDecl RdrName]
              -> [LImportDecl RdrName]
-- Consruct the implicit declaration "import Prelude" (or not)
--
-- NB: opt_NoImplicitPrelude is slightly different to import Prelude ();
-- because the former doesn't even look at Prelude.hi for instance
-- declarations, whereas the latter does.
mkPrelImports this_mod loc implicit_prelude import_decls
  | this_mod == pRELUDE_NAME
   || explicit_prelude_import
   || not implicit_prelude
  = []
  | otherwise = [preludeImportDecl]
  where
      explicit_prelude_import
       = notNull [ () | L _ (ImportDecl { ideclName = mod
                                        , ideclPkgQual = Nothing })
                          <- import_decls
                      , unLoc mod == pRELUDE_NAME ]

      preludeImportDecl :: LImportDecl RdrName
      preludeImportDecl
        = L loc $ ImportDecl { ideclSourceSrc = Nothing,
                               ideclName      = L loc pRELUDE_NAME,
                               ideclPkgQual   = Nothing,
                               ideclSource    = False,
                               ideclSafe      = False,  -- Not a safe import
                               ideclQualified = False,
                               ideclImplicit  = True,   -- Implicit!
                               ideclAs        = Nothing,
                               ideclHiding    = Nothing  }

parseError :: DynFlags -> SrcSpan -> MsgDoc -> IO a
parseError dflags span err = throwOneError $ mkPlainErrMsg dflags span err

--------------------------------------------------------------
-- Get options
--------------------------------------------------------------

-- | Parse OPTIONS and LANGUAGE pragmas of the source file.
--
-- Throws a 'SourceError' if flag parsing fails (including unsupported flags.)
getOptionsFromFile :: DynFlags
                   -> FilePath            -- ^ Input file
                   -> IO [Located String] -- ^ Parsed options, if any.
getOptionsFromFile dflags filename
    = Exception.bracket
              (openBinaryFile filename ReadMode)
              (hClose)
              (\handle -> do
                  opts <- fmap (getOptions' dflags)
                               (lazyGetToks dflags' filename handle)
                  seqList opts $ return opts)
    where -- We don't need to get haddock doc tokens when we're just
          -- getting the options from pragmas, and lazily lexing them
          -- correctly is a little tricky: If there is "\n" or "\n-"
          -- left at the end of a buffer then the haddock doc may
          -- continue past the end of the buffer, despite the fact that
          -- we already have an apparently-complete token.
          -- We therefore just turn Opt_EtaDoc off when doing the lazy
          -- lex.
          dflags' = gopt_unset dflags Opt_EtaDoc

blockSize :: Int
-- blockSize = 17 -- for testing :-)
blockSize = 1024

lazyGetToks :: DynFlags -> FilePath -> Handle -> IO [Located Token]
lazyGetToks dflags filename handle = do
  buf <- hGetStringBufferBlock handle blockSize
  unsafeInterleaveIO $ lazyLexBuf handle (pragState dflags buf loc) False blockSize
 where
  loc  = mkRealSrcLoc (mkFastString filename) 1 1

  lazyLexBuf :: Handle -> PState -> Bool -> Int -> IO [Located Token]
  lazyLexBuf handle state eof size = do
    case unP (lexer False return) state of
      POk state' t -> do
        -- pprTrace "lazyLexBuf" (text (show (buffer state'))) (return ())
        if atEnd (buffer state') && not eof
           -- if this token reached the end of the buffer, and we haven't
           -- necessarily read up to the end of the file, then the token might
           -- be truncated, so read some more of the file and lex it again.
           then getMore handle state size
           else case t of
                  L _ ITeof -> return [t]
                  _other    -> do rest <- lazyLexBuf handle state' eof size
                                  return (t : rest)
      _ | not eof   -> getMore handle state size
        | otherwise -> return [L (RealSrcSpan (last_loc state)) ITeof]
                         -- parser assumes an ITeof sentinel at the end

  getMore :: Handle -> PState -> Int -> IO [Located Token]
  getMore handle state size = do
     -- pprTrace "getMore" (text (show (buffer state))) (return ())
     let new_size = size * 2
       -- double the buffer size each time we read a new block.  This
       -- counteracts the quadratic slowdown we otherwise get for very
       -- large module names (#5981)
     nextbuf <- hGetStringBufferBlock handle new_size
     if (len nextbuf == 0) then lazyLexBuf handle state True new_size else do
       newbuf <- appendStringBuffers (buffer state) nextbuf
       unsafeInterleaveIO $ lazyLexBuf handle state{buffer=newbuf} False new_size


getToks :: DynFlags -> FilePath -> StringBuffer -> [Located Token]
getToks dflags filename buf = lexAll (pragState dflags buf loc)
 where
  loc  = mkRealSrcLoc (mkFastString filename) 1 1

  lexAll state = case unP (lexer False return) state of
                   POk _      t@(L _ ITeof) -> [t]
                   POk state' t -> t : lexAll state'
                   _ -> [L (RealSrcSpan (last_loc state)) ITeof]


-- | Parse OPTIONS and LANGUAGE pragmas of the source file.
--
-- Throws a 'SourceError' if flag parsing fails (including unsupported flags.)
getOptions :: DynFlags
           -> StringBuffer -- ^ Input Buffer
           -> FilePath     -- ^ Source filename.  Used for location info.
           -> [Located String] -- ^ Parsed options.
getOptions dflags buf filename
    = getOptions' dflags (getToks dflags filename buf)

-- The token parser is written manually because Happy can't
-- return a partial result when it encounters a lexer error.
-- We want to extract options before the buffer is passed through
-- CPP, so we can't use the same trick as 'getImports'.
getOptions' :: DynFlags
            -> [Located Token]      -- Input buffer
            -> [Located String]     -- Options.
getOptions' dflags toks
    = parseToks toks
    where
          getToken (L _loc tok) = tok
          getLoc (L loc _tok) = loc

          parseToks (open:close:xs)
              | IToptions_prag str <- getToken open
              , ITclose_prag       <- getToken close
              = map (L (getLoc open)) (words str) ++
                parseToks xs
          parseToks (open:close:xs)
              | ITinclude_prag str <- getToken open
              , ITclose_prag       <- getToken close
              = map (L (getLoc open)) ["-#include",removeSpaces str] ++
                parseToks xs
          parseToks (open:close:xs)
              | ITdocOptions str <- getToken open
              , ITclose_prag     <- getToken close
              = map (L (getLoc open)) ["-haddock-opts", removeSpaces str]
                ++ parseToks xs
          parseToks (open:xs)
              | ITdocOptionsOld str <- getToken open
              = map (L (getLoc open)) ["-haddock-opts", removeSpaces str]
                ++ parseToks xs
          parseToks (open:xs)
              | ITlanguage_prag <- getToken open
              = parseLanguage xs
          parseToks _ = []
          parseLanguage (L loc (ITconid fs):rest)
              = checkExtension dflags (L loc fs) :
                case rest of
                  (L _loc ITcomma):more -> parseLanguage more
                  (L _loc ITclose_prag):more -> parseToks more
                  (L loc _):_ -> languagePragParseError dflags loc
                  [] -> panic "getOptions'.parseLanguage(1) went past eof token"
          parseLanguage (tok:_)
              = languagePragParseError dflags (getLoc tok)
          parseLanguage []
              = panic "getOptions'.parseLanguage(2) went past eof token"

-----------------------------------------------------------------------------

-- | Complain about non-dynamic flags in OPTIONS pragmas.
--
-- Throws a 'SourceError' if the input list is non-empty claiming that the
-- input flags are unknown.
checkProcessArgsResult :: MonadIO m => DynFlags -> [Located String] -> m ()
checkProcessArgsResult dflags flags
  = when (notNull flags) $
      liftIO $ throwIO $ mkSrcErr $ listToBag $ map mkMsg flags
    where mkMsg (L loc flag)
              = mkPlainErrMsg dflags loc $
                  (text "unknown flag in  {-# OPTIONS_GHC #-} pragma:" <+>
                   text flag)

-----------------------------------------------------------------------------

checkExtension :: DynFlags -> Located FastString -> Located String
checkExtension dflags (L l ext)
-- Checks if a given extension is valid, and if so returns
-- its corresponding flag. Otherwise it throws an exception.
 =  let ext' = unpackFS ext in
    if ext' `elem` supportedLanguagesAndExtensions
    then L l ("-X"++ext')
    else unsupportedExtnError dflags l ext'

languagePragParseError :: DynFlags -> SrcSpan -> a
languagePragParseError dflags loc =
  throw $ mkSrcErr $ unitBag $
     (mkPlainErrMsg dflags loc $
       vcat [ text "Cannot parse LANGUAGE pragma"
            , text "Expecting comma-separated list of language options,"
            , text "each starting with a capital letter"
            , nest 2 (text "E.g. {-# LANGUAGE TemplateHaskell, GADTs #-}") ])

unsupportedExtnError :: DynFlags -> SrcSpan -> String -> a
unsupportedExtnError dflags loc unsup =
  throw $ mkSrcErr $ unitBag $
    mkPlainErrMsg dflags loc $
        text "Unsupported extension: " <> text unsup $$
        if null suggestions then Outputable.empty else text "Perhaps you meant" <+> quotedListWithOr (map text suggestions)
  where
     suggestions = fuzzyMatch unsup supportedLanguagesAndExtensions


optionsErrorMsgs :: DynFlags -> [String] -> [Located String] -> FilePath -> Messages
optionsErrorMsgs dflags unhandled_flags flags_lines _filename
  = (emptyBag, listToBag (map mkMsg unhandled_flags_lines))
  where unhandled_flags_lines = [ L l f | f <- unhandled_flags,
                                          L l f' <- flags_lines, f == f' ]
        mkMsg (L flagSpan flag) =
            ErrUtils.mkPlainErrMsg dflags flagSpan $
                    text "unknown flag in  {-# OPTIONS_GHC #-} pragma:" <+> text flag
